JP2001283824A - Lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium secondary battery with a high productivity enabling a stable large-current discharge, by curtailing collecting resistance from an inner electrode body. SOLUTION: A lithium secondary battery is provided with an inner electrode body 1 with a cathode plate 2 and an anode plate 3 wound round and laminated through a separator 4. A plurality of collecting tabs 5A, 5B fitted to either the cathode plate 2 or the anode plate 3 are connected to inner terminals of the cathode and the anode, respectively, or are connected together at least at one place of the inner terminals of the cathode and the anode so that tips of the collective tabs form a slanting face, and at the same time, at least the slanting face of the collecting tabs is welded and jointed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention is excellent in productivity,
The present invention relates to a lithium secondary battery capable of performing stable large-current discharge by reducing current collection resistance from an internal electrode body.

[0002]

2. Description of the Related Art In recent years, in response to the demand for emission control of carbon dioxide and the like against the background of a growing environmental protection movement, the automobile industry has replaced electric vehicles (EVs) with vehicles using fossil fuels such as gasoline vehicles. Hybrid electric vehicle (H
There is a growing movement to promote the introduction of EVs.

[0003] EV and HEV batteries are required not only to have a large battery capacity but also to have a large battery output that greatly affects the acceleration performance and the climbing performance of a vehicle.
From such required characteristics, a lithium secondary battery is considered to be the most suitable battery among batteries currently in practical use.

Generally, an internal electrode body of a lithium secondary battery is wound or wound so that a positive electrode plate and a negative electrode plate do not come into direct contact with each other via a separator made of a porous polymer film. It is configured by lamination. For example, as shown in FIG. 7, the wound internal electrode body 1 is manufactured by winding a positive electrode plate 2 and a negative electrode plate 3 with a separator 4 interposed therebetween, and the positive electrode plate 2 and the negative electrode plate 3 (hereinafter, referred to as “ Electrode plates 2 and 3 "
That. ), A current collecting tab 5A for the positive electrode and a current collecting tab 5B for the negative electrode (hereinafter, referred to as "tabs 5A and 5B") are provided.

[0005] Then, the electrode plates 2 of the tabs 5A and 5B
The other end connected to 3 is attached to a current extraction terminal 12 such as an external terminal 16 or an internal terminal member 11 that is electrically connected to the external terminal 16. That is, the tabs 5A and 5B are
While collecting current from the electrode plates 2 and 3, the current extraction terminal 1
It has a role as a lead wire that conducts to the second.

The external terminal refers to an electrode terminal for extracting current to the outside of the battery, the internal terminal member refers to a member for temporarily collecting current inside the battery, and the current extracting terminal refers to these. It is a generic term. Therefore,
It is also possible to integrate the external terminal and the internal terminal member to form a current extraction terminal.

The electrode plates 2 and 3 are formed by using a metal foil such as aluminum for the positive electrode plate 2 and a metal foil such as copper for the negative electrode plate 3 as a current collecting substrate, and applying an electrode active material to each of them. The tabs 5A and 5B are provided on at least one side of such a current collecting board. Therefore, tabs 5A and 5
When a strip-shaped material is used as B, when winding the electrode plates 2 and 3, shape irregularities such as partial bulging toward the outer periphery at the tabs 5A and 5B are less likely to occur. This is preferable because the contact resistance between the electrode and the current collecting tab can be reduced.

[0008]

[Problems to be Solved by the Invention] EV or HEV
It is assumed that a large amount of current such as 100 A or 200 A needs to frequently flow per battery in a lithium secondary battery. In order to reduce the output loss of the battery when such a large current flows, it is necessary to minimize the internal resistance of the entire battery. In a lithium secondary battery, the current-collecting resistance generated when extracting current from the internal electrode body is one of the major internal resistance factors.To reduce it, as described above, a plurality of strip-shaped current-collecting tabs are used. Some ideas have been devised for use and for welding a plurality of current collecting tabs without high resistance.

Therefore, as one of the measures, Japanese Patent Application Laid-Open No. 9-92335 discloses a configuration in which the tips of a plurality of strip-shaped current collecting tabs are aligned at the tip end surface. A method of connecting to the internal terminals of the positive electrode and the negative electrode and welding the current collecting tab with a laser from a parallel side, and a method of welding the current collecting tab with a ultrasonic wave from a side perpendicular to the current collecting tab. According to this welding method, a battery can be joined in a wide area, the internal resistance is low, and a battery excellent in large current discharge characteristics is obtained. However, in this method, since the welding is performed from the parallel or right angle side of the aligned current collecting tabs, the surface irradiated by the laser or the like melts well, but the melting condition of the inner part drops remarkably. This means that uneven welding cannot be avoided. That is, it cannot be welded to such an extent that the plurality of current collection tabs and the plurality of current collection tabs and the internal terminals are integrated,
It cannot be said that the current collecting resistance is low. Therefore, large current discharge is frequently performed, and it is completely unsuitable for applications such as electric vehicles that require low internal resistance. In addition, when each of the current collecting tabs is connected to the internal terminal, the tabs are connected to the entire periphery of the internal terminal, so the work efficiency when welding is poor, and considering the actual manufacturing process, With this connection method, mechanical automation is difficult.

[0010]

Means for Solving the Problems The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to tilt the tip of a current collecting tab to cope with large current discharge. An object of the present invention is to provide a lithium secondary battery in which a wide area is uniformly welded by welding the inclined surfaces thereof in a state where the lithium secondary batteries are arranged side by side and the current collecting resistance is reduced.

That is, according to the present invention, a lithium secondary battery using a non-aqueous electrolyte and an internal electrode body obtained by winding or laminating a positive electrode plate and a negative electrode plate with a separator interposed therebetween,
A plurality of strip-shaped current collecting tabs attached to the positive electrode plate or the negative electrode plate are respectively connected to the internal terminals of the positive electrode and the negative electrode, and the tip of the current collecting tab is configured to have an inclined surface. A lithium secondary battery is provided, wherein at least an inclined surface of the tab is welded.

Further, according to the present invention, there is provided a lithium secondary battery using an internal electrode body and a non-aqueous electrolyte obtained by winding or laminating a positive electrode plate and a negative electrode plate with a separator interposed therebetween.
A plurality of strip-shaped current collecting tabs attached to the positive electrode plate or the negative electrode plate are collectively connected to at least one of the internal terminals of the positive electrode and the negative electrode, and the tip of the current collecting tab is formed as an inclined surface. And a lithium secondary battery characterized in that at least the inclined surface of the current collection tab is welded.

Here, the welding of the current collecting tabs includes:
Laser welding and / or electron beam welding is preferably performed. In the case where the thickness of one current collecting tab is 5 μm or more and 100 μm or less, and at least 20 current collecting tabs are joined. It is preferably used.

[0014] By applying a roller with an R to the inclined surface of the current collecting tab, the tips of the current collecting tabs may be aligned in an inclined manner. It can be exposed, which is preferable from the viewpoint of ease of welding and workability. The lithium secondary battery of the present invention is suitably employed for a battery having a battery capacity of 2 Ah or more, and preferably having a plurality of current collection tabs per electrode plate. Further, it is preferably used as an on-vehicle battery, and is suitably used as a power source for starting an engine requiring high output, a power source for driving a motor of an electric vehicle or a hybrid electric vehicle in which a large current is frequently discharged.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The lithium secondary battery of the present invention
A current extraction member that uses an internal electrode body with a plurality of current collection tabs, welds a wider area of the current collection tab more uniformly, reduces current collection resistance, and improves reliability. is there. Hereinafter, an embodiment of the present invention will be described,
It goes without saying that the present invention is not limited to the following embodiments.

In the lithium secondary battery of the present invention, as shown in FIG. 1, a plurality of strip-shaped current collecting tabs attached to a positive electrode plate or a negative electrode plate are connected to internal terminals of a positive electrode and a negative electrode, respectively. The tip of the tab is configured to have an inclined surface, and at least the inclined surface of the current collecting tab is welded.

When the tip of the current collecting tab is configured to have an inclined surface, the tip of each current collecting tab is always uniformly exposed. Therefore, when the inclined surface is irradiated with a laser or the like as described later, it is inevitable. Preferably, each of the tip portions is irradiated and welded, and the entire current collecting tab can be easily integrated, so that the resistance distribution of the current collecting tab does not fluctuate and the current collecting resistance is greatly reduced, which is preferable. "Welding at least the inclined surface" means that the current collecting resistance can be made sufficiently low by welding the inclined surface, but also includes the case where the side surface of the current collecting tab is welded. It is a broad concept.

Further, in the lithium secondary battery of the present invention, a plurality of strip-shaped current collecting tabs attached to the positive electrode plate or the negative electrode plate are collectively connected to at least one of the internal terminals of the positive electrode and the negative electrode. The tip of the current tab is configured to have an inclined surface, and at least the inclined surface of the current collecting tab is welded.

FIGS. 2A, 2B, and 2 C show the current collecting tab.
As shown in (c), if the parts are gathered in one place or several places, only the gathered positions of the current collecting tabs 5A and 5B need to be welded, so that the workability of welding is improved,
In addition, mechanical automation can be easily performed. In addition, since the present invention is configured such that the tips of the current collecting tabs 5A and 5B are inclined surfaces, even if the current collecting tabs are put together, all of the tips are uniformly exposed. That is, a wide range of the current collecting tab can be uniformly welded.

In the conventional method of connecting the current collecting tabs to the internal terminals, in a state where the front ends of the current collecting tabs are uniformly aligned on the front end surface, 1) each of the current collecting tabs is connected to the internal terminal 22A.・ Connect to 22B and connect each to current collecting tabs 5A ・ 5
B, that is, in parallel with the stacking direction of the
A method of irradiating a laser or the like aiming at the current collecting tabs from the side surface of the device, or as shown in FIG.
Similarly, a method of irradiating a laser or the like in parallel to the direction of lamination of the current collecting tabs at a place or about two places is adopted.

According to the method 1), the tip is exposed more frequently than when collecting the tabs at several places in a state where the tips of the current collecting tabs 5A and 5B are evenly aligned on the tip surfaces. Therefore, the degree of welding to the internal terminals is improved accordingly. However, when welding, the internal terminals 22A and 22B
The work efficiency is not good because it is necessary to fix the tab with the tab presser and to weld each part around the entire circumference of the work. Also, since not all of the ends of the current collecting tabs are exposed, welding cannot be performed until a plurality of current collecting tabs are integrated. In the method 2), even if a laser or an electron beam with good penetration of the tab is used, as shown in FIG. 4, penetration away from the irradiation surface decreases and uniform welding is difficult. ,Also,
This limits the number of tabs to be welded.

The lithium secondary battery of the present invention is a driving battery for an electric vehicle or a hybrid electric vehicle. Since a large current flows, the internal resistance of the battery is preferably as small as possible. Therefore, it is important that the current collecting resistance from the internal electrode body is as small as possible, and it is sometimes desired to increase the number of current collecting tabs as necessary. From this viewpoint as well, there is a limit to the method of connecting the current collecting tabs to the internal terminals and welding them in a state in which the front ends of the current collecting tabs are uniformly aligned on the front end surface.

On the other hand, if the tip of the current collecting tab of the present invention is configured to have an inclined surface, even if the number of tabs is large, as shown in FIG. There is no limit on the number of tabs. In a lithium secondary battery having a wound electrode body, the number of current collecting tabs 5A and 5B is often 50 or more in consideration of current collecting resistance. Even with this number, if the tip of the current collector is an inclined surface, it is possible to uniformly weld all the current collecting tabs, but the inclined surface is formed on a longer surface, and the welding is also performed. In addition, it becomes inevitably more difficult to uniformly form the tip of the current collecting tab with an inclined surface by using a roller with R described later.

Therefore, when the number of tabs is large, as shown in FIG. 2, it is preferable that the current collecting tabs 5A and 5B are combined at a plurality of locations and connected to the internal terminals 22A and 22B. It is preferable to collect the data from two places to about four places in accordance with the above.

In the present invention, the current collecting tab is preferably welded using laser welding and / or electron beam welding. In the laser welding and the electron beam welding, current collecting tabs 5A and 5 bundled with the internal terminal member 11 are used.
It is possible to uniformly melt and weld the metal of the entire B, thereby making it possible to extremely reduce the contact resistance between the current collecting tabs 5A and 5B and the internal terminal members and to generate a small amount of heat. Has features. By making this feature and the front end surface of the current collecting tab an inclined surface, welding can be performed before each current collecting tab is integrated, and the current collecting resistance can be reduced.

In laser welding and electron beam welding, as shown in FIG. 5, the current collecting tab is aimed at from a direction parallel to the main plane of the current collecting tabs 5A and 5B, that is, from the upper end face of the current collecting tab. When irradiating a laser or the like, parallel to the stacking direction of the current collecting tabs, that is, when irradiating a laser or the like aiming at the current collecting tab from the side surface of the current collecting tab, and tilting the current collecting tab therebetween in an oblique direction. The same good welding can be obtained even when irradiating in the range up to when irradiating laser etc.

When performing welding, the current collecting tab 5A
-Since one end of 5B is connected to the internal electrode body 1, easy handling of the internal electrode body 1, danger of fusing the current collecting tabs 5A and 5B, heat to the internal electrode body 1 It is preferable to consider the welding workability, including matters such as damage to the internal electrode body 1 due to transmission.

A current collecting tab 5 that is preferable for applying the present invention
The thickness and the number of A.5B are not limited to the conditions described above, but the thickness of one of the current collecting tabs 5A and 5B is 5 μm.
It is preferable to use those having a size of m to 100 μm,
The present invention has a remarkable effect when at least 20 current collecting tabs 5A and 5B are joined.

In the present invention, it is preferable that the inclined surface of the current collecting tab is one in which the tip of the current collecting tab is inclined and aligned by applying a roller 25 with an R. At the time of welding, as shown in FIG. 6 (a), when a roller with an R is pressed from the side to the current collecting tabs 5A and 5B extending from the wound electrode body, each current collecting tab is pressed. Since the lengths of 5A and 5B are uniform, in the electrode body, the current collecting tab inside the winding is long and the current collecting tab outside is sequentially short, and as shown in FIG. It becomes a uniform inclined surface. By doing so, the tip of the current collecting tab can be made an inclined surface with high work efficiency, and welding can be easily performed.

The lithium secondary battery of the present invention uses a strip-shaped current collecting tab in order to extract the current of the internal electrode body. Therefore, there are no restrictions on other materials or battery structures. Hereinafter, the main members constituting the battery and the structure thereof will be outlined.

In the internal electrode body of the lithium secondary battery (hereinafter, referred to as “battery”) of the present invention, the positive electrode plate and the negative electrode plate are directly connected to each other via a separator made of a porous polymer film. It is wound or laminated so as not to come into contact with. Generally, the wound internal electrode body 1 is formed by winding a positive electrode plate 2 and a negative electrode plate 3 with a separator 4 interposed therebetween, as shown in FIG.
3, current collecting tabs 5A and 5B are provided respectively.

On the other hand, as shown in FIG. 8, the laminated internal electrode body 7 alternately laminates a positive electrode plate 8 and a negative electrode plate 9 with a separator 10 interposed therebetween, and forms positive and negative electrode plates 8.
It is called “electrode plates 8 and 9”. ) Are connected to a current collecting tab 6A for the positive electrode and a current collecting tab 6B for the negative electrode.

Each of the positive electrode plates 2 and 8 and the negative electrode plates 3 and 9 is formed in a thin plate shape by applying each electrode active material to a current collecting substrate. Examples of the form of the current collecting substrate include foil and mesh. In the present invention, an aluminum foil is used as the current collecting substrate for the positive electrode plates 2 and 8, and a copper foil is used as the current collecting substrate for the negative electrode plates 3 and 9. Are preferably used.

In any of the batteries having any of the above structures, generally, as a positive electrode active material, lithium cobalt oxide (LiCoO ₂ ) or lithium nickel oxide (L
iNiO ₂ ) or lithium manganate spinel (Li
For example, a lithium transition metal composite oxide such as Mn ₂ O ₄ ) is used. In addition, in order to improve the conductivity of these positive electrode active materials, it is also preferable to mix carbon powder such as acetylene black or graphite powder with the electrode active material. on the other hand,
As the negative electrode active material, an amorphous carbonaceous material such as soft carbon or hard carbon, or a carbonaceous powder such as natural graphite or artificial graphite is used.

As the separators 4 and 10, those having a three-layer structure in which a lithium-ion permeable polyethylene film having micropores is sandwiched between porous lithium-ion permeable polypropylene films are preferably used. When the temperature of the internal electrode body rises, the polyethylene film softens at about 130 ° C. and the micropores are crushed, which also serves as a safety mechanism for suppressing the movement of lithium ions, that is, the battery reaction. By sandwiching the polyethylene film between polypropylene films having a higher softening temperature, contact and welding between the electrode plates 2 and 3 and between the electrode plates 8 and 9 can be prevented.

As described above, the present invention has mainly been described with reference to an example in which a wound electrode body is used. However, it goes without saying that the present invention does not matter on the battery structure. The lithium secondary battery is preferably used for a battery having a relatively large battery capacity, preferably using a plurality of current collecting tabs. Specifically, a wound or laminated electrode body 1.7
Is suitably used for batteries having a battery capacity of 2 Ah or more. It goes without saying that the use of the battery is not limited, but as a large-capacity vehicle-mounted battery that requires high output, low internal resistance and excellent cycle characteristics, it can be used for starting an engine or for an electric vehicle or hybrid electric vehicle. It can be particularly suitably used for driving motors of automobiles.

[0037]

As described above, according to the present invention, a plurality of current collection tabs are configured such that the tip ends have inclined surfaces, and at least the inclined surfaces are welded to uniformly weld a wide area of the current collection tabs. As a result, a large current can be discharged stably. As a result, the lithium secondary battery of the present invention is:
An excellent effect of improving the large current discharge characteristics, facilitating the manufacture, and improving the reliability is achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a lithium secondary battery of the present invention.

FIG. 2 is a schematic diagram of a top surface and a cross section showing one embodiment of tab welding in the lithium secondary battery of the present invention.

FIG. 3 is a schematic view of a top surface and a cross section showing one embodiment of tab welding in a conventional lithium secondary battery.

FIG. 4 is a schematic view showing a state of welding in a current collecting tab configured so that tips are uniformly arranged.

FIG. 5 is a schematic view showing a state of welding in a current collecting tab having a front end configured to be an inclined surface.

6 (a) and 6 (b) are diagrams illustrating a method of forming a current collecting tab on an inclined surface in the lithium secondary battery of the present invention.

FIG. 7 is a perspective view showing an embodiment of a structure of a wound internal electrode body.

FIG. 8 is a perspective view showing one embodiment of a structure of a laminated internal electrode body.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wound type electrode body, 2 ... Positive electrode plate, 3 ... Negative electrode plate, 4 ... Separator, 5A * 6A ... Positive current collecting tab, 5B * 6B ... Negative current collecting tab, 7 ... Laminated electrode body, 8 ... Positive electrode plate, 9 ... Negative electrode plate, 10 ... Separator, 11 ... Internal terminal member, 12 ...
Current extraction terminal, 13: winding core, 14: battery, 15A ...
Positive electrode cover, 15B: negative electrode cover, 16A: positive external terminal, 16
B: negative electrode external terminal, 17: elastic body, 18: pressure release hole, 19
... Metal foil, 20 ... Pressure release valve, 21 ... Crimping part, 22A ... Positive electrode internal terminal, 22B ... Negative electrode internal terminal, 23 ... Insulating polymer film, 24 ... Battery case, 25 ... Roller, 2
6 ... Weld.

Continued on the front page F term (reference) 5H022 AA09 BB01 BB11 BB16 BB17 CC02 CC12 CC19 CC20 CC24 5H029 AJ02 AJ06 AJ14 AK03 AL06 AM03 AM04 AM05 AM07 BJ02 BJ14 CJ03 CJ05 DJ05 DJ12 HJ12 HJ19

Claims (9)

[Claims] 1. A lithium secondary battery using a non-aqueous electrolyte and an internal electrode body obtained by winding or laminating a positive electrode plate and a negative electrode plate with a separator interposed therebetween. A plurality of strip-shaped current collection tabs to be attached are connected to the internal terminals of the positive electrode and the negative electrode, respectively, and the tip of the current collection tab is configured to have an inclined surface, and at least the inclined surface of the current collection tab is welded. A lithium secondary battery characterized by the following. 2. A lithium secondary battery using a non-aqueous electrolyte and an internal electrode body obtained by winding or laminating a positive electrode plate and a negative electrode plate with a separator interposed therebetween. A plurality of strip-shaped current collecting tabs to be attached are collectively connected to at least one of the internal terminals of the positive electrode and the negative electrode, and the tip of the current collecting tab is configured to have an inclined surface. A lithium secondary battery having at least an inclined surface welded. 3. The lithium secondary battery according to claim 1, wherein the current collecting tab is welded by laser welding and / or electron beam welding. 4. The current collection tab according to claim 1, wherein the thickness of one of the current collection tabs is 5 μm or more and 100 μm or less, and at least 20 current collection tabs are joined.
4. The lithium secondary battery according to claim 3. 5. The current collector tab according to claim 1, wherein the inclined surface is provided with a roller having an R, so that a tip of the current collecting tab is inclined. 4. The lithium secondary battery according to 1. 6. The lithium secondary battery according to claim 1, wherein the battery capacity is 2 Ah or more. 7. The lithium secondary battery according to claim 1, wherein the lithium secondary battery is a vehicle-mounted battery. 8. The lithium secondary battery according to claim 7, which is used for an electric vehicle or a hybrid electric vehicle. 9. The lithium secondary battery according to claim 7, which is used for starting an engine.